This invention relates to the preparation of nitriles and more in particular it relates to the production of monomeric N-methyleneaminoacetonitrile.
The previously known N-methyleneaminoacetonitrile trimer has been used as an intermediate for many reactions where glycinonitrile is useful, such as the production of glycine or the manufacture of imino diacetic acid. It has the advantage that it is more stable than glycinonitrile and thus has a better shelf life. It is also less soluble in water thus facilitating recovery from the reaction medium. It has been found that the monomeric compound of this invention has similar utility and advantages to the trimer and is simpler to produce.
N-methyleneaminoacetonitrile trimer, also called N-methylene glycinonitrile (trimer) has previously been prepared by several different routes. A classical procedure for the preparation of the trimer is that described by Klages in J. prakt. Chem. (2), 65, 192 (1902). At the time, Klages believed the product to be the dimer. There is further confusion in the literature as the trimer product has often been named as the monomer. This particular preparative method is not attractive commercially because it involves the use of an expensive intermediate, glycinonitrile hydrochloride.
N-methyleneaminoacetonitrile trimer has also been prepared by the reaction of formaldehyde, an ammonium halide and an alkali metal cyanide in the presence of acid as described by Jay and Curtius, Ber. 27, 59 (1894) and later, by Adams and Langley, Organic Synthesis, Coll. Vol. I, 347 (1932). Recently, an improvement upon this basic process was described in U.S. Pat. No. 2,823,222.
U.S. Pat. No. 3,167,581, issued Jan. 26, 1965 suggests a continuous preparation of trimeric N-methyleneaminoacetonitrile directly from formaldehyde, hydrogen cyanide and ammonia. See also U.S. Pat. Nos. 3,256,314 and 3,096,362 for other prior art processes.
However, the above processes produce products which are the trimer of N-methyleneaminoacetonitrile and not the monomer. The trimeric products have a melting point of about 129.degree. C. and have the characteristic infrared spectrum shown in FIG. 2. In contradistinction, the process of this invention is directed to the production of the hitherto unknown monomeric form. This unique product has a melting point of about 167.degree.-170.degree. C. and the infrared spectrum shown in FIG. 1.